Though irrelevant in most cases of interest, there is a clear physical inconsistency in all the above-mentioned problems: they tacitly assume that information on the position of the merchant vessel reaches the pirate ship instantly, i.e. that whatever signal used by the pirates to infer the merchants' position (such as light or sound) travels at infinite speed. Nonetheless, it is a well-known consequence of Einstein's theory of relativity that nothing can travel faster than the speed of light in empty space. [1]}
